Tribological performance of industrial applications involving boundary lubrication regime can be improved by depositing surface coatings such as diamond-like carbon (DLC) on the interacting surfaces. DLCs are considered as hard coatings with unique combination of properties which results in minimizing the friction induced energy and material losses especially under starved lubrication conditions. In spite of high wear-resistance and ultralow friction coefficients, there are a lot of factors that can directly influence the tribological characteristics of DLC coatings. Although, many studies were conducted to comprehend the effects of intrinsic/extrinsic conditions on tribological behavior of these coatings, still there is a lack of understanding due to contradictory remarks. Therefore, there is a need to rearrange the published data in an organized manner for logical continuation of research. In this paper, a brief introduction of DLC coatings is presented followed by detailed discussion on conditions that can directly influence their tribological properties.

In this study, surface texturing and hydrogenated amorphous carbon (a-C:H) diamond-like carbon (DLC) coating was combined to evaluate the coating performance at various temperatures in oil lubricated reciprocating sliding tests. Micro dimples were created by laser surface texturing on M2 steel using a Pico second laser. DLC coating was deposited by hybrid magnetron sputtering on textured substrates. Textured a-C:H showed stable coefficient of friction at 30, 80, and 125 °C compared to un-textured a-C:H. At 30 °C, graphitization was not observed for both textured and un-textured DLC coating. Graphitization was more pronounced in the case of un-textured a-C:H at 80 and 125 °C. Results show that, at all temperatures tested (30–125 °C), DLC textured samples showed higher wear resistance compared to un-textured DLC coating. The improvement in wear resistance can be explained by the lower graphitization of textured DLC coating. Lower graphitization in the case of textured DLC might be due to the wear particle capturing and lubricant retention ability of textures.

Wear and corrosion exist as one of the main important factor of energy and material losses in mechanical and chemical process. Coating is classified as one of the ways to enhance energy, chemical, and mechanical durability. Several previous investigations reported that addition of nanoparticle as an additive will enhance the characteristic of surface roughness and wear properties. The objective of this study is to investigate the wear, surface roughness, and corrosion resistance of Co–Ni–Fe nanoparticles electrodeposited on mild steel. The effect of deposition time toward physical properties (composition, surface morphology, and surface roughness), hardness, corrosion, and slurry wear erosion properties of coated mild steel were investigated. The finding showed that the increase of the deposition time led to an increment of hardness and coating thickness. The optimum Co–Ni–Fe nanoparticles deposited at 30 min produced a uniform coating and microhardness of 277.42 HV. Besides, the cumulative coating mass loss obtained from 30 min deposited coating sample was the lowest at both rotational speeds of 300 and 1200 rpm. It was observed that the optimum deposition time improved the surface roughness, coating morphology, hardness and resistance toward slurry erosion and corrosion.

Single- and multi-layer amorphous carbon (a-C) films of varying thickness were deposited on Si(100) substrates by radio-frequency sputtering in a pure Ar atmosphere. The thickness, roughness, coefficient of friction, and residual stress of the a-C films were measured by profilometry, atomic force microscopy, surface force microscopy, and curvature method, respectively. The through-thickness nanostructure and elemental composition of the films were examined by cross-sectional transmission electron microscopy and electron energy loss spectroscopy. The multi-layer a-C films, consisting of alternating ∼10-nm-thick hard and soft a-C layers deposited under 0 and −200 V substrate bias, respectively, were found to exhibit lower roughness, coefficient of friction, and residual stress and slightly higher tetrahedral carbon atom hybridization than single-layer a-C films of similar thickness. The results of this study reveal a strong correlation of the friction characteristics with the surface roughness and nanostructure of single- and multi-layer a-C films.

This paper investigates friction and wear between an electro-deposited coating and high carbon chrome steel. A ball-on-flat plate tribometer was developed, measuring tangential and normal displacements of a high carbon chrome steel ball. For the purpose of measuring displacements of a ball, laser displacement sensors were used. An electro-deposited coating was applied to a cold-rolled high strength steel plate. Displacement amplitudes of 0.2 and 1.0 mm were imposed to produce fretting and reciprocal sliding at contact. A steady-state value of the kinetic friction coefficient between an electro-deposited coating and high carbon chrome steel was found to be about 0.28. It was identified that wear volume on a coated specimen increased with the number of cycles. Correlation between the wear volume and a normal displacement of a ball was found to be linear. It was demonstrated that the proposed method is useful for understanding friction and wear of an electro-deposited coating.

A carbide cutting tool is widely used in machining process due to its availability and being cheaper than a better performance cutting tool, such as cubic boron nitride. The carbide cutting tool also has substantial hardness and toughness that is suitable to be applied in intermittent cutting. This paper presents the case study of a wear mechanism experienced on the cutting edge of the coated and uncoated carbide tools in turning and milling processes. The wear mechanisms of carbide cutting tools were investigated in machining Inconel 718, titanium alloy Ti–6Al–4V extra-low interstitial, and aluminum metal matrix composite (AlSi/AlN MMC) at their high cutting speed regime. The tools failed primarily due to wear on the flank and rake faces. The failure mode of the carbide cutting tools was similar regardless of the machining operations and coating is believed to enhance the tool life, but once removed, the tool fails similar to that with the uncoated tool.

Titanium carbonitride (TiCN) is a popular hard coating for carbide cutting tools in various applications. This paper studied the influence of the carbon content and coating composition within TiCxN1−x coatings with regard to their adhesive strength on tungsten carbide substrate and subsequently, the performance of cutting tool in the dry turning of stainless steel. Among all the TiCxN1−x coatings, the TiCN coating has exhibited the highest adhesivity onto a substrate, followed by a TiC coating and lastly, a TiN coating. It was found that the adhesive strength of TiCN coating increased with the carbon content. The C/N ratio or C–N bond is a vital contributor to the adhesivity of the TiCxN1−x coating rather than the C or N atoms in the TiCxN1−x coating. It was found that the coating was delaminated before the exposure of substrate material. Hence, coating with higher adhesivity will promote longer tool life.

Tribology is a phenomenon concerning the relative motion between at least two amalgamating surfaces. In the machining process, surface roughness is the most important element for studying this occurrence, which contributes to the evaluation of part quality. This paper will provide detailed analysis for better understanding of tribological during the machining process of Inconel 718 alloy using a multi-layer TiAlN/AlCrN-coated carbide ball end inserted in dry cutting condition. The analysis focused on the relationship of tool wear with cutting temperature, cutting force, and surface integrity. Results found that the cutting temperature increased around 7.5% and surface roughness of machined surface improved about 10.3% when the cutting speed increased. Flaking at the rake face and notching at the flank face were determined as the main tool failures during milling Inconel 718. Furthermore, high friction between the tool–workpiece interfaces during machining was due to the build-up edge (BUE) formation that causes an alteration in microstructure at machine surface.

Carbon fiber reinforced plastic (CFRP) is an expensive composite which has become valuable material as the demand for this composite increased in the industries. It is suitable to be used in automotive, aerospace, and aircraft because of its properties which is stronger than steel and also stiffer than titanium while retaining its lighter weight. However machining of CFRP is a mess to machinist due to its nature which is abrasive. The paper presents the wear mechanism on solid carbide cutting tool during milling CFRP. The wear mechanism is observed under dry and chilled air machining. The machining parameters tested were at cutting speed of 200 m/min with constant feed rate and depth of cut. For both dry and chilled air machining, it is observed that carbide cutting tool experienced abrasive wear which has been influenced by abrasive powdering chips and fibers during milling CFRP. Under microscope and scanning electron microscope, the abrasive wear is represented by shiny and polish area on the cutting tool respectively. This abrasive wear is observed higher under dry machining compared to the chilled air machining which was due to the heat generated during machining. Thus, chilled air has a potential of improving machinability of CFRP by using solid carbide cutting tool.

In the recent years, carbon fiber reinforced polymer (CFRP) composites have formed a very important class of tribo-engineering materials in nonlubricated condition. The usage of CFRPs has been growing at a substantial rate that leads to the increasing amount of waste generated from end-of-life components and manufacturing scrap. In the present paper, the role of as-received (rCF-AR) and cryogenic treated (rCF-T) recycled carbon fiber (rCF) reinforcements were investigated on the tribological behavior of epoxy composites by using a micro pin-on-disc tribotester apparatus under dry sliding condition. The wear behavior of the composites was analyzed based on three different sliding velocities and loads at a constant sliding distance. The results showed that the reinforcement effect of rCF-T as compared to rCF-AR has enhanced the wear resistance of epoxy composite, which is attributed to the improved adhesion between the treated rCFs and epoxy matrix.

Incineration or disposal of carbon fiber waste from the aircraft industry leads to serious energy consumption and environmental pollution. The use of this waste as reinforcement is a wise approach to appreciate the high performance of the carbon fiber. In this study, the sliding wear and frictional behavior of recycled carbon fiber prepreg (rCFP) reinforced polypropylene (PP) prepared via melt compounding method using an internal mixer were studied. The samples were categorized into PP reinforced by carbon fiber with resin (A) and carbon fiber without resin (B). Pin-on-disc method was utilized to evaluate the effect of rCFP content and physical condition of fibers on tribological performance of the composites. The results were supported by morphological analyses using scanning electron microscopy. It was found that polymer composites B for rCFP without resin exhibited better tribological performance than composites category-A. The addition of rCFP into PP was observed to increase its wear resistance with minimum coefficient of friction achieved at 3 wt% of rCFP content for both polymer composites.

We present a comprehensive nanoscale tribological characterization of single-layer graphene grown by chemical vapor deposition (CVD) and transferred onto silicon oxide (SiO2) substrates. Specifically, the nanotribological properties of graphene samples are studied via atomic force microscopy (AFM) under ambient conditions using calibrated probes, by measuring the evolution of friction force with increasing normal load. The effect of using different probes and post-transfer cleaning procedures on frictional behavior is evaluated. A new method of quantifying lubrication performance based on measured friction coefficient ratios of graphene and SiO2 is introduced. A comparison of lubrication properties with mechanically-exfoliated graphene is performed. Results indicate that CVD-grown graphene constitutes a very good solid lubricant on SiO2, reducing friction coefficients by ∼90% for all investigated samples. Finally, the effect of wrinkles associated with CVD-grown graphene on measured friction values is quantitatively analyzed, with results revealing a substantial increase in friction on these structural defects.

The role of bottom-up and top-down synthesis methods on the nanotribological response of few layer graphene (FLG) in air and various liquid environments is reported. Oxidized FLG adhesion against Si increases by a factor of 2 as compared to non-oxidized samples. Also, it is reported that the FLG center-to-edge adhesion typically exhibits a decreasing tendency. In air, a highly lubricious nanotribological response (0.03–0.04) of both bottom-up and top-down prepared samples is measured. The frictional behavior of bottom-up synthesized FLG in different liquid environments is found to depend on the absence or presence of viscous aggregates in the respective liquid. A Stribeck-like behavior is suggested for viscous synthetic lubricants, such as silicone, present as the third body in the FLG/Si tip system. Such nanoscale behavior, indicating transitions in different lubrication regimes, may be particularly important for the further understanding of liquid–graphene interfaces in novel tribological and device applications.

This paper investigates the effects of graphene nanoplatelets (GNPs) as additives in palm-oil trimethylolpropane (TMP) ester blended in polyalphaolefin. Different concentrations of GNPs that were ultrasonically homogenized in blended lubricants consist of 95 vol% polyalphaolefin and 5 vol% TMP ester. Physical properties of the nanolubricants were identified and tribological behaviors of GNP in blended lubricants were studied using standard fourball testing and surface analysis was done on the wear surfaces using scanning electron microscopy and energy-dispersive x-ray techniques. Addition of 0.05 wt% GNP in blended lubricant resulted in the lowest coefficient of friction and wear scar diameter, thus selected as the most suitable concentration of GNP in the blended lubricant. Friction and wear were reduced by 5 and 15% respectively, with the presence of 0.05 wt% GNP in the blended lubricant.

Thermal degradation of graphene based mineral oil lubricants was studied using thermogravimetric analysis (TGA). As-synthesized graphene sheets of 8, 12, and 60 nm thick and engine oil formulations 20W50 SN/CF and 20W50 SJ/CF were used for synthesizing various test samples. UV-Vis spectrophotometry, zeta potential, field emission scanning electron microscopy, and energy-dispersive x-ray spectroscopy were used to characterize the graphene sheets and the nanolubricants. TGA revealed that the onset temperature of oxidation for the SN/CF oil could be delayed by 13–17 °C in the presence of graphene. Moreover the rate of oxidation when the weight loss of oil in the presence of graphene reaches 40–20% could be delayed by more than 30 °C. Resistance to oil degradation depends strongly on the graphene nanoparticle size and concentration. TGA kinetics studies show that the base oils have higher activation energy (Ea) and the addition of graphene significantly reduces Ea.

Graphene is a 2D carbon allotrope that has attracted significant attention because its properties have a wide range of applications. Graphene was deposited on the polycrystalline nickel substrate with a dimension of 0.10 mm × 10 mm × 10 mm via thermal chemical vapor deposition (TCVD). The natural carbon source was obtained from a commercial palm oil as a carbon precursor. The D, G, and 2D bands described the vibration of graphitic layer and overtone of the D band at 1352, 1594, and 2716 cm−1, respectively. The lowest G band full width at half maximum (FWHM) was 38.7 cm−1 at 900 °C deposition temperature. In the x-ray diffraction (XRD) pattern, the FWHM of Ni (200) peak was 0.38°. Raman spectroscopy, UV–vis spectrophotometry, atomic force microscopy, XRD, and field emission scanning electron microscopy characterized the synthesized graphene. Multilayer graphene was successfully synthesized from the palm oil via TCVD.

Thick coatings of tetrahedral amorphous carbon (ta-C) have great existing and potential commercial importance for components such as automobile accessories. We confirmed the feasibility of depositing thick ta-C coating on Si wafer, WC, stainless steel (STS), and Al alloy substrates by a home-made filtered cathode vacuum arc. A ta-C coating of 800 nm thickness was successfully deposited over 20 min continuous coating. Interestingly, coatings with thicknesses exceeding 1 μm were easily delaminated by thermal and internal stress effects when the coating time exceeded 20 min. Varying the bias (0 V ↔ 500 V) was highly effective in controlling the internal stress relaxation of the ta-C. This method showed significant improvements in the stress relaxation of the ta-C coatings. By applying multicycle coating, the thickness and hardness of the ta-C coating could reach 9.3 μm and 45 GPa, respectively, at a coating speed of 3.0 μm/h on a fixed substrate.

Nanocrystalline diamond films have been deposited by pulsed electron beam ablation from a single target and on different substrates at room temperature and under argon background gas at 0.5 Pa. The films have been deposited from a highly ordered pyrolytic graphite target on four different substrate materials, which include silicon, stainless steel, sapphire, and cubic boron nitride. Based on experimental measurement data, obtained from various analytical techniques, it has been observed that sp3 bonded carbon content, grain size, film roughness, and nanocrystalline fraction of the films do not seem to be much affected by the type of substrate material used. The thickness of the films, in the range of ∼70–90 nm, seems to be relatively the same irrespective of the substrate material. Hardness measurements have shown that film hardness, ranging between 18.5 and 19.5 GPa, is not remarkably influenced by the type of substrate material.

The development of energy storage device utilizing carbon nanomaterials possesses remarkably significant electrochemical performance. As compared to others, carbon nanomaterials including carbon black, graphene, activated carbon, and carbon nanotube have advantages in ion accessibility and specific surface area in which, more charged ions can access and transfer to the surfaces of material and thus have enhanced electrical charge storage performance. This manuscript briefly reviews the deposition of carbon nanomaterials from electrophoretic deposition technique which is good because of its simple, economical, versatility, and possibility of the thin film deposition on large substrate. The current state-of-the-art and performance of devices employing carbon as electrode material is also extensively discussed.